Lenses for correcting vision may be spherical, to correct the focus of the eye for near and far distances, or cylindrical or "toric", to correct an astigmatism of the eye.
Dies for molding plastic corneal contact lenses are generally know. Typically, the dies include a mold member made of steel and having an end face ground and polished to extremely precise specifications. Two mold members, one having a convex end face and the other having a concave end face, are juxtaposed to define a mold cavity which is subsequently filled with plastic material by injection molding to form a contact lens.
Conventional dies for forming plastic contact lenses have a fixed geometry so that, for variations in toricity, different dies must be employed. Thus, according to the prior art, a different mold member having a different, permanently shaped end face would be required for differently powered lenses.
An example of a prior art mold member is described in U.S. Pat. No. 3,871,813 to Cappeli. The patent describes a specific method of grinding and thus forming a convex surface on the end face of a mold member.